1. Field of the Invention
The present invention relates to a throttle control system of an engine for use in the throttle opening control system for a vehicle, for example, such as acceleration slip control system, constant running hold system, idling control system, automatic speed control system and fuel cost control system.
2. Description of the Related Art
Japanese patent laid open publication No. Sho-61-272423 discloses a throttle control system for a vehicle combining a constant running hold system and an acceleration slip control system. This system comprises an input member being reciprocated around a pivot axis by an accelerator control means. An output member drives a throttle valve by being reciprocated around a coaxial pivot axis by an actuator and includes an intermediate member for transmitting reciprocation of the input member to the output member by reciprocating around the coaxial pivot axis, and a spring arrangement for connecting the output member and the intermediate member. The throttle valve is manually operated by the accelerator operator, at the same time, the accelerator operator is driven by the actuator in constant speed running mode and acceleration slip control mode.
However, the aforementioned conventional throttle control system employs a complicated mechanism in order to restrict the throttle valve opening and closing operation for constant speed running control and throttle valve closing operation for acceleration slip control which may simultaneously function by operational error.
The aforementioned actuator is provided with two parallel operating arrangements with each set including speed reducing a mechanism and an electromagnetic clutch as well as a one way clutch. Each speed reducing mechanism is driven by a common motor, and a common output member is driven by each of the one way clutches It is constructed so as to connect the respective electromagnetic clutches during acceleration slip control and constant speed running control. Use of such complicated actuator mechanisms has increased the likelihood of failure in addition to the problem of manufacturing costs.